The invention relates to a disc brake and more particularly to a disc brake of the type comprising a caliper or frame member straddling a rotary disc and slidable on a fixed member by means of two circumferentially spaced guide keys, actuating means being associated with the caliper or frame member so as to urge directly a first friction pad and, by reaction, a second friction pad on to the respective faces of the disc, each of the keys being associated with one of the said members and comprising a guiding surface which slidably cooperates with a corresponding surface of the other member, means being provided to permit pivoting of the caliper or frame member in a plane perpendicular to the disc and passing through the circumferentially spaced guide keys.
The invention also relates to a guide key for use in a brake of this type.
Brakes of the type defined are generally called floating caliper or floating-frame brakes.
In this type of brake, the caliper can pivot slightly in a plane perpendicular to the disc, so that it compensates automatically for slight warping of the disc or for any lack of parallelism between the axis of the disc and the direction of caliper sliding as defined by the guide surfaces of the keys.
The means permitting pivoting of the caliper forming member are usually provided at the sliding surfaces, which are reduced to lines of contact. With such an arrangement, however, impurities can easily slip between the sliding surfaces, so that after prolonged use of the brake the caliper forming member may be unable to slide relative to the fixed support member.